The ＂Three-North＂ Shelterbelt is the largest and most distinctive artificial ecological engineering project in China. It has been conducted since November 25, 1978 in the ＂Three-North＂ （i.e., Northeast China, North China and Northwest China） regions. In this study, the background and the essential benefits of the ＂Three-North＂ Shelterbelt project are summarized. The basic status and future development of the ＂Three-North＂ Shelterbelt project are also studied. As well, we tried to discuss the problems existing in the current shelterbelt system and the strategies to conduct this ecological project rationally.
LI Miao-miaoLIU An-tianZOU Chun-jingXU Wen-duoHideyuki SHIMIZUWANG Kai-yun
Cinnamomum camphora （L.） Presl is an evergreen broad-leaved tree of the Lauraceae family, widely distributed in the sub-tropical areas in the south of China and used as a virescent tree in urban gardens and streets in Shanghai for its beautiful shape and intensive stress-resistance. However, yellowing of C camphora in recent years casts doubt about its significance. We believe the green-leaved and yellow-leaved C camphora might be two different ecotypes, and tentatively refer to the green-leaved C camphora as C camphora f. viridis f. nov （CCV） and the yellow-leaved as C camphora f.flavus f. nov （CCF）. We studied their differences and arrived at the following conclusions： 1） compared with CCF, the area of lamina of CCV is significantly larger and the amount of chlorophyll （Chl） significantly higher; 2） the lamina and palisade tissues of CCV are significantly thicker than those of CCF, but its cuticle is significantly thinner; 3） the shape of the stomata of CCV is different from that of the CCF; the stomatal density and stomatal index of CCV are significantly lower than those of CCF. These results show that C camphora might evolve adaptive dif- ferentiation in some aspects which can be used in virescence in urban streets and gardens.
